?PROJECT 3 Social inequalities related to race, ethnicity and socioeconomic (SES) status lead to spatial patterning in neighborhood risk factors, where certain groups such as Hispanics are disproportionately exposed to environmental hazards (e.g., air pollution, toxic releases) and place-based social stressors such as crime, poverty and deprivation. This ?double jeopardy? contributes to their increased susceptibility and to persistent maternal health disparities, with Hispanics at a significant disadvantage compared to whites in terms of pregnancy-related maternal morbidity and mortality and access to postpartum health care. Pregnancy and early postpartum years are also a time of high residential mobility (i.e., address moves), which is important to capture to better inform exposure assessment of not only the residence but also the full geographic and temporal context around it, including the built, physical and chemical environment which may also contribute to health disparities. One health indicator thought to contribute to increased susceptibility within disparity populations is allostatic load (AL), where allostasis refers to the body?s multisystemic ability to regulate internal physiology in response to actual and anticipated objective or perceived stressors. The AL model posits that repeated, chronic exposure to hazards and stressors can dysregulate the body?s adaptive systems leading to ?wear and tear? on organ systems and negative outcomes over the life course, such as cardiovascular, cognitive and stress-related diseases, with important racial and ethnic differences. Air pollution, social stressors and neighborhood socioeconomic deprivation have all been associated with AL. Yet very few studies have investigated the contribution of joint exposure to environmental hazards and social stressors during pregnancy and postpartum on AL, particularly in racial and ethnic minorities and low SES groups. Our project interrogates this question in our recently established MADRES pregnancy cohort of predominantly low income, Hispanic women in Los Angeles, CA. We aim to first understand distinct patterns in neighborhood and residential environmental exposures and social stressors in relation to residential mobility during pregnancy and postpartum, and then investigate their effects on maternal AL as an early indicator of stress maladaptation in the first four years postpartum. In addition, we will investigate whether individual-level characteristics such as demographics, psychosocial stressors and acculturation modify these effects using a multilevel framework. Our proposed project will contribute to advancing the science of environmental health disparities by providing a scientific basis for how the environment interacts with social stressors across multiple levels to impact physiological mechanisms that may signal early stress maladaptation and increased risk before onset of disease in disparity populations.